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VOLUME 5, ISSUE 1 

 2022 

 

RESEARCH ARTICLE 

Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics 

& Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

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https://doi.org/10.33137/cpoj.v5i1.36847


 

1 

Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics & 
Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

 

 

 
RESEARCH ARTICLE 

 

EFFECTS OF UNITY PROSTHETIC ELEVATED VACUUM SUSPENSION SYSTEM ON MINIMUM 

SWING TOE CLEARANCE 

Gholizadeh H1 , Lemaire E.D1,2, Nantel J3* 

 

1 Centre for Rehabilitation Research and Development, Ottawa Hospital Research Institute, Ottawa, Canada. 
2 Department of Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Canada.  
3 School of Human Kinetics, Faculty of Health Sciences, University of Ottawa, Ottawa, Canada. 

 

 

 

 

  

 

 

 

 

 

 

 

 
 

INTRODUCTION   

The vertical distance between the swinging foot’s toe region 

and the ground is defined as minimum swing toe clearance 

(MSTC) and is a critical gait parameter since it is linked to 

tripping risk.1,2 MSTC in able-bodied individual during level 

walking is approximately 13 mm, and is sensitive to swing 

leg ankle, knee, and hip angles.1,3,4 People with transtibial 

amputation have higher risk of tripping and falling than able-

bodied individuals, which could be due to prosthetic 

component malfunction, or poor proprioception. Literature 

showed any failure in prosthetic suspension system or 

restricted ankle dorsiflexion may decrease toe clearance in 

lower limb amputees.5-7  

Pistoning between the residual limb and prosthetic socket5,8 

during swing can affect prosthetic length, which could cause 

insufficient MSTC.5-7 Choosing an appropriate prosthetic 

suspension system to connect the residual limb to the 

socket is a vital step in the rehabilitation process, leading to 

improved fit inside the socket and decreased pistoning.9-10  

Elevated vacuum suspension systems could decrease the 

pistoning between the residual limb and socket9-12 

compared to other prosthetic suspension systems, and 

therefore improve MSTC.  

In our previous research, we assessed the effect of Össur’s 

Unity Figure 1 elevated vacuum suspension system 

(https://assets.ossur.com/library/33281/Unity) on gait 

 
OPEN  ACCESS Volume 5, Issue 1, Article No.1. 2022 

 

 

Journal Homepage: https://jps.library.utoronto.ca/index.php/cpoj/index 

 

ABSTRACT 

BACKGROUND: The risk of tripping in people with amputation is greater than that of able-bodied 

individuals due to reduced toe clearance during the swing phase. Appropriate prosthetic suspension 

may increase toe clearance by providing more secured attachment between the residual limb and 

prosthetic socket. Research is lacking on the Unity suspension system's effect on swing toe clearance. 

METHODS: Twelve people with transtibial amputation were fitted with the Unity suspension system. 

After one month accommodation period, the person walked with active (ON) or inactive vacuum (OFF) 

in a CAREN-Extended virtual reality system, across multiple simulated real-world scenarios. Prosthetics 

minimum swing toe clearance, and kinematic data, while the vacuum was ON or OFF, were compared 

with the intact side and a group of 12 able-bodied individuals.   

RESULTS: Minimum swing toe clearance (MSTC) and knee flexion angle were larger on the prosthetic 

side (active and inactive vacuum) compared to both the intact side and the control group. However, hip 

flexion angle on the prosthetic side was approximately 17% smaller than the control group. Unlike the 

control group, MSTC with active and inactive vacuum suspension was not significantly different between 

level walking and other walking conditions. Finally, among all walking conditions, the lowest swing toe 

clearance for both control and the amputee groups was recorded when the limb was at the top of a 

side-slope.  

CONCLUSION: An effective suspension system could improve toe clearance; however, significant 

differences were not found between active and inactive vacuum conditions. The likelihood of 

inappropriate foot contact on side-slope ground might be greater than other walking conditions for both 

able-bodied and amputee groups, possibly leading to stumbling or falling. 

ARTICLE INFO 

Received: June 21, 2021 

Accepted: October 6, 2021 

Published: October 23, 2021 

CITATION 

Gholizadeh H, Lemaire E.D, 

Nantel J. Effects of unity 

prosthetic elevated vacuum 

suspension system on minimum 

swing toe clearance. Canadian 

Prosthetics & Orthotics Journal. 

2022; Volume 5, Issue 1, No.1. 

https://doi.org/10.33137/cpoj.v5i1.

36847 

KEYWORDS 

Prosthesis, Rehabilitation, Lower 

Limb Amputation, Gait, Toe 

Clearance, Transtibial Prosthesis, 

Mobility, Prosthetic Suspension, 

Amputation 

 

 

* CORRESPONDING AUTHOR 

Julie Nantel, PhD  

School of Human Kinetics, Faculty of Health Sciences,  

University of Ottawa, Ottawa, Canada, K1N 6N5 

Email: jnantel@uottawa.ca 

ORCID ID: https://orcid.org/0000-0001-7253-9222 

https://doi.org/10.33137/cpoj.v5i1.36847
https://assets.ossur.com/library/33281/Unity
https://jps.library.utoronto.ca/index.php/cpoj/index
https://doi.org/10.33137/cpoj.v5i1.36847
https://doi.org/10.33137/cpoj.v5i1.36847
mailto:jnantel@uottawa.ca
https://orcid.org/0000-0001-7253-9222


 

2 

Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics & 
Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

ISSN: 2561-987X 
EFFECTS OF PROSTHETIC SUSPENSION SYSTEM ON SWING TOE CLEARANCE 

Gholizadeh et al., 2022 CPOJ 

 
parameters while the vacuum was active or inactive.13-15 

We found significant differences between vacuum 

conditions for some gait parameters, but differences were 

small and may not be clinically relevant. However, step 

length symmetry between intact and prosthetic limbs 

improved with active elevated vacuum.  

 

Figure 1: Unity suspension system. 

The effects of Össur’s Unity suspension system on MSTC 

when walking on community-relevant surfaces with 

continuous perturbations have not yet been studied and this 

paper addresses that cap. Walking over non-level surfaces 

is more challenging than level walking, especially for people 

with transtibial amputation as they must continually adapt 

their movement patterns due to the increased 

biomechanical demands of continuously variable 

terrain.13,14,16 In addition, more challenging walking 

conditions, may require higher cognitive demand compared 

to level walking, which could lead to a more cautious gait 

pattern.17,18 Therefore, the purpose of this study was to 

evaluate the effects of the system on MSTC and kinematics 

at the hip, knee and ankle during gait across multiple 

simulated real-world walking scenarios by comparing the 

prosthetic side, with active and inactive vacuum 

suspension, to the intact limb. Moreover, MSTC and gait 

kinematics were compared between the amputee group and 

12 able-bodied individuals for the first time in this study. We 

hypothesized that statistically significant differences will 

occur between able-bodied participants and the transtibial 

amputation group regarding MSTC and ankle, knee and hip 

angles, across all walking conditions. Moreover, Unity users 

are hypothesized to have larger MSTC on the intact side 

compared to the prosthetic side with active (ON) or inactive 

vacuum (OFF). We also hypothesized that positive 

correlations would occur between MSTC and ankle, knee, 

and hip angles during different walking conditions. This 

study can enhance clinicians' and prescribers' 

understanding of Unity suspension system’s effects on 

MSTC, which can help provide safe mobility for people with 

limb loss. 

METHODOLOGY 

A convenience sample of 12 active people with unilateral 

transtibial amputation (11 males, 1 female) who used their 

prosthesis daily was recruited from The Ottawa Hospital 

Rehabilitation Centre. The participant’s mean height was 

178.3 (SD=6.4) cm, weight was 90.6 (SD=16.4) kg, age was 

57.2 (SD=15.3) years, and time since amputation was 13.1 

(SD=20.0) years. Data from a group of 12 able-bodied 

individuals (11 males, 1 female) from our databases were 

compared with the amputee group. Control group mean 

height was 176.6 (SD=7.8) cm; weight was 81.4 (SD=11.0) 

kg; and age was 38.3 (SD=10.6) years. The Ottawa Hospital 

Research Ethics Board approved the study protocol and all 

participants provided written informed consent.    

2.1. Data collection  

A new prosthesis with an Iceross Seal-In V liner and a Pro-

flex XC foot with Unity pump was fabricated for each 

participant and after one month acclimation period, three-

dimensional motion analysis was collected in the CAREN 

Extended virtual reality lab. Participants walked at their own 

comfortable self-selected walking speed and completed 

walking trials with vacuum inactive (OFF) or active (ON). 

The order of active and inactive vacuum was randomized 

and blinded for the participants. The average self-selected 

walking speed were 1.07 (SD: 0.23) and 1.03 (SD: 0.20) m/s 

for inactive and active vacuum respectively. This 

methodology has been described in detail in our previous 

publications.13-15 The average self-selected walking speed 

for the control group was slightly higher (mean: 1.29 (SD: 

0.06) m/s). Each walking trial was 340 m that included: level 

walking; down slope (7° decline); up slope (7° incline); right 

and left slopes (5° slope); medial-lateral translations 

(platform oscillates in the medial-lateral direction); hilly 

(platform oscillates in the sagittal plane); and rocky 

conditions. Right and left slopes were separated into top 

cross-slope (TS) and bottom cross-slope (BS). During right 

slope, the right limb was at the bottom of the slope and the 

left limb was at the top. During left slope, the right limb was 

at the top and the left limb was at the bottom of the slope.  

2.2. Data Analysis 

Vicon Nexus software version 2.3 (Vicon, Oxford UK) and 

Visual3D software version 6 (C-Motion, Germantown, MD) 

were used for gait analysis. Helen Hayes markers set was 

used in this study. Heel (posterior and lateral side), 5th 

metatarsal head, and 2nd metatarsal head makers were 

secured to the shoes. The 5th metatarsal marker was used 

to track the toe position (toe marker). Minimum toe marker 

position during swing phase of gait was determined and 

subtracted from the baseline (toe marker position during the 

mid-stance) to calculate MSTC. Also, hip, knee, and ankle 

https://doi.org/10.33137/cpoj.v5i1.36847


 

3 

Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics & 
Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

ISSN: 2561-987X 
EFFECTS OF PROSTHETIC SUSPENSION SYSTEM ON SWING TOE CLEARANCE 

Gholizadeh et al., 2022 CPOJ 

 
angles were determined at the point of MSTC. Data were 

analyzed using Microsoft Excel (version 2010) and SPSS 

(version 23.0). Shaprio-Wilk tests were used to evaluate 

data normality and p<0.05 was considered statistically 

significant. One-way repeated measures ANOVAs were 

used to find the effect of walking condition on each variable. 

A one-way ANOVA with a Bonferroni adjustment for multiple 

comparisons was used to compare between prosthetic (ON, 

OFF) and intact side and data from 12 able-bodied 

individuals (control group). Pearson's correlation 

coefficients (Pearson’s R) were used to determine the 

strength of linear relationship between MSTC and the joint 

angle at the ankle, knee and hip.   

RESULTS 

Mean and standard deviation of MSTC and hip, knee, and 

ankle angles at the time of MSTC are presented in Table 1. 

Descriptive statistics showed that MSTC, knee, and hip 

angle were mostly greater on the prosthetic side (ON and 

OFF) than on the intact side (Table 1). MSTC and knee 

angle were greater on the prosthetic side (vacuum ON and 

OFF) than able-bodied individuals; however, prosthetic hip 

angle was smaller. Maximum MSTC and knee angle 

occurred during down slope for both vacuum conditions. 

However, in the able-bodied group, maximum MSTC 

occurred during rocky and knee angle occurred during up 

slope walking. Maximum hip angle occurred during up slope 

walking for both amputee and able-bodied groups. Lowest 

MSTC occurred when the limb was at the top of the cross-

slope, for all participants. Much larger differences were 

found between knee and hip angles for amputees than able-

bodied individuals. For example, the largest differences 

between knee and hip angles during down slope walking 

were approximately 22 degrees for amputees (prosthetic 

side-vacuum ON) compared to 11 degrees for able-bodied 

participants.   

One-way repeated measures ANOVA showed no significant 

MSTC differences between level walking and other walking 

conditions in the transtibial amputation group (both 

prosthetic and intact sides) (Table 2, Figure 2). However, in 

the able-bodied group, MSTC during level walking was 

significantly smaller than other walking conditions except 

top cross-slope (Table 2). Hip angle was significantly 

different (p<0.001) between level walking and up slope 

walking, for prosthetic and intact sides (vacuum ON and 

OFF). However, able-bodied group hip angle during level 

walking was significantly different than other conditions, 

except bottom cross-slope. 

One-way ANOVA results (Table 3) showed significant 

differences (p<0.05) between the control group and Unity 

 

Table 1: Mean and Standard Deviation (in brackets) of minimum swing toe clearance (MSTC, cm) and ankle, knee, and hip angles (degrees) 

at the time of MSTC. Walking conditions are LW: Level; DS: Down slope; US: Up slope; HL: Hilly; TS: Top cross-slope; BS: Bottom cross-

slope; ML: Medio-Lateral; RO: Rocky.   

 
Walking 

conditions 

INTACT LIMB PROSTHETIC LIMB 

MSTC Ankle  Knee  Hip  MSTC Ankle  Knee  Hip  

1
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LW 1.9 (0.8) 2.2 (2.5) 25.4 (5.5) 16.4 (7.2) 2.2 (0.9) 

3.0 (1.6) 

31.4 (4.0) 19.1 (6.9) 

DS 2.5 (0.8) 2.8 (2.6) 31.1 (5.9) 14.6 (8.3) 3.1 (0.5) 38.9 (6.6) 17.4 (7.8) 

US 2.1 (0.9) 7.0 (2.8) 34.5 (7.9) 29.5 (9.8) 2.3 (0.9) 35.6 (6.2) 32.9 (9.9) 

HL 1.8 (0.4) 1.9 (1.8) 26.4 (4.6) 17.9 (7.9) 2.6 (0.5) 32.0 (6.6) 20.3 (8.3) 

TS 1.2 (0.9) 4.2 (2.7) 29.4 (5.5) 20.4 (7.6) 1.6 (0.6) 33.3 (7.5) 22.1 (8.0) 

BS 2.4 (0.7) 0.6 (2.4) 24.0 (5.5) 15.0 (7.9) 2.8 (0.6) 30.0 (3.8) 17.8 (7.1) 

ML 1.8 (0.6) 2.2 (2.1) 26.1 (5.1) 17.7 (8.0) 2.2 (0.7) 30.9 (5.0) 20.0 (8.0) 

RO 2.1 (0.6) 1.7 (2.5) 27.5 (5.0) 18.5 (7.8) 2.7 (0.5) 32.1 (4.8) 20.9 (7.6) 

Average 
(SD) 

2.0 (0.4) 2.8 (2.0) 28.1 (3.4) 18.8 (4.7) 2.4 (0.5)   33.0 (2.9) 21.3 (4.9) 

V
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LW 2.1 (1.2) 2.8 (3.2) 25.7 (4.6) 17.3 (7.6) 2.4 (1.1) 

3.0 (1.6) 

31.7 (6.2) 19.6 (7.1) 

DS 2.7 (1.2) 3.2 (3.3) 30.8 (3.6) 15.2 (8.5) 3.2 (0.7) 38.0 (7.2) 17.5 (8.2) 

US 2.8 (1.3) 7.8 (2.7) 37.6 (6.7) 31.5 (7.9) 2.6 (1.1) 36.7 (7.0) 33.6 (8.5) 

HL 2.4 (1.4) 2.6 (3.7) 27.2 (5.5) 18.7 (8.8) 2.8 (1.4) 32.5 (6.3) 20.4 (8.2) 

TS 1.3 (0.5) 4.6 (3.0) 29.6 (5.6) 20.6 (7.5) 1.8 (0.4) 33.0 (6.5) 23.0 (7.5) 

BS 2.6 (0.6) 1.0 (2.8) 24.6 (4.6) 15.6 (7.1) 3.0 (0.8) 30.8 (6.0) 18.4 (7.0) 

ML 2.2 (1.3) 3.0 (3.1) 26.9 (5.5) 17.9 (7.9) 2.5 (1.1) 31.0 (6.0) 20.3 (7.7) 

RO 2.3 (0.6) 2.9 (3.0) 28.4 (5.5) 18.9 (7.7) 3.0 (0.5) 31.0 (3.8) 20.3 (8.1) 

Average 
(SD) 

2.3 (0.5) 3.5 (2.0) 28.9 (4.1) 19.5 (5.2) 2.7 (0.4)   33.1 (2.8) 21.6 (5.1) 

 

        

1
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LW 1.6 (0.4) 0.3 (2.0) 25.4 (5.1) 23.1 (5.0) 

 

DS 2.4 (0.6) 1.4 (2.7) 29.3 (6.3) 18.7 (6.3) 

US 2.6 (0.8) 7.3 (3.4) 38.8 (4.5) 38.7 (5.9) 

HL 2.6 (0.5) 1.1 (2.4) 28.6 (5.4) 25.7 (5.8) 

TS 1.4 (0.5) 1.6 (1.9) 27.5 (5.7) 26.2 (5.5) 

BS 2.5 (0.6) -1.4 (2.2) 24.3 (4.3) 22.7 (4.9) 

ML 2.2 (0.6) 0.8 (2.3) 27.0 (4.4) 25.1 (5.2) 

RO 2.9 (0.9) 1.7 (3.0) 28.7 (5.3) 26.6 (6.0) 

Average 
(SD) 

2.3 (0.5) 1.6 (2.5) 28.7 (4.4) 25.9 (5.8) 

 

https://doi.org/10.33137/cpoj.v5i1.36847


 

4 

Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics & 
Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

ISSN: 2561-987X 
EFFECTS OF PROSTHETIC SUSPENSION SYSTEM ON SWING TOE CLEARANCE 

Gholizadeh et al., 2022 CPOJ 

 
users (vacuum ON and OFF) for MSTC and knee angle 

during down slope walking (Table 3). Knee angle was 

significantly different between groups for level and bottom 

cross-slope conditions. During level walking, MSTC was 

greater (p=0.041) for Unity users (vacuum OFF) than the 

control group. 

Pearson correlation coefficients were low between MSTC 

and ankle, knee, and hip in able-bodied individuals during 

different walking conditions (Table 4). Correlations were also 

low between MSTC and hip angle in people with transtibial 

amputation, on both prosthetic and intact sides (vacuum ON 

and OFF). Low correlations were found between MSTC and 

knee angle on the prosthetic side when vacuum was ON. 

High correlations were found between MSTC and knee 

angle during hilly and medio-lateral walking when the 

vacuum was OFF (prosthetic side). A strong correlation was 

found between MSTC and ankle angle during level walking 

and down-slope walking on the intact side when vacuum 

was ON. Moderate and strong correlations were also found 

between MSTC and ankle angle during different walking 

conditions on the intact side (vacuum OFF) (Table 4). 

DISCUSSION 

In this research, we evaluated the effects of the Unity 

elevated vacuum suspension system on MSTC during gait. 

All people in this study had acceptable MSTC, which 

allowed their feet to clear the ground safely when walking 

across multiple simulated real-world walking scenarios. 

Overall, MSTC and knee angles were larger and hip angles 

were smaller on the prosthetic side (vacuum ON and OFF) 

than the able-bodied individuals. Different from the control 

group, no significant MSTC differences were found between 

level walking and other walking conditions, in the amputee 

group for both prosthetic and intact sides (vacuum ON and 

OFF). Unexpectedly, we found no statistically significant 

differences between vacuum ON and OFF conditions for 

MSTC, knee, and hip angles.  

For the able-bodied group, MSTC was approximately 1.6 

cm during level walking, which was similar to the previously 

reported results.2,3,19 Similar to findings by Sinitski et al.,20  

in amputees, MSTC was greater on the prosthetic side 

(vacuum ON and OFF) than the intact side and greater than 

results from able-bodied individuals for most of walking 

conditions. This outcome differed from the previous 

literature where the absence of a controllable prosthetic 

ankle joint caused insufficient MSTC, thereby potentially 

increasing tripping risk.6,21,22 Furthermore, Gates et al., 

(2012) found that MSTC in people with transtibial 

amputation was 1.3 times greater on the intact side than the 

prosthetic side.17 Johnson et al., (2014) suggested that 

using a prosthetic foot with a hydraulic ankle joint could 

provide adequate toe clearance (2.2 cm) during level 

walking.6 The current study showed that using Unity 

suspension system could also provide similar MSTC to 

allow the foot to clear the ground safely during level walking.  

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https://doi.org/10.33137/cpoj.v5i1.36847


 

5 

Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics & 
Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

ISSN: 2561-987X 
EFFECTS OF PROSTHETIC SUSPENSION SYSTEM ON SWING TOE CLEARANCE 

Gholizadeh et al., 2022 CPOJ 

 
Table 3: P values for comparisons between amputee group 

(prosthetic side) and able-bodied group; A= able-bodied; B= Unity 

ON; C= Unity OFF. Bold signifies a significant difference. Walking 

conditions are LW: Level; DS: Down slope; US: Up slope; HL: Hilly; 

TS: Top cross-slope; BS: Bottom cross-slope; ML: Medio-Lateral; 

RO: Rocky. 

  (A,B) (A,C) (B,C) 

LW 

MSTC 0.316 0.041 1.000 

Knee Angle 0.024 0.017 1.000 

Hip Angle 0.413 0.571 1.000 

DS 

MSTC 0.028 0.007 1.000 

Knee Angle 0.004 0.010 1.000 

Hip Angle 1.000 1.000 1.000 

US 

MSTC 1.000 1.000 1.000 

Knee Angle 0.630 1.000 1.000 

Hip Angle 0.296 0.433 1.000 

HL 

MSTC 1.000 1.000 1.000 

Knee Angle 0.532 0.381 1.000 

Hip Angle 0.274 0.281 1.000 

TS 

MSTC 0.811 0.148 1.000 

Knee Angle 0.126 0.156 0.515 

Hip Angle 0.498 0.827 1.000 

BS 

MSTC 0.936 0.312 1.000 

Knee Angle 0.019 0.007 1.000 

Hip Angle 0.220 0.355 1.000 

ML 

MSTC 1.000 1.000 1.000 

Knee Angle 0.226 0.202 1.000 

Hip Angle 0.265 0.316 1.000 

RO 

MSTC 1.000 1.000 1.000 

Knee Angle 0.252 0.746 1.000 

Hip Angle 0.186 0.125 1.000 

 

Figure 2: Minimum Swing Toe Clearance in different walking 

conditions. A comparison between the Unity (vacuum ON and OFF) 

and Able-bodied group. 

This might be due to improved proprioception and socket fit 

(less pistoning inside the socket) with the Iceross Seal-In V 

liner.15   

Literature shows that people adopt a more cautious gait 

pattern while walking on more challenging walking 

conditions.13,14,16 Moreover, Merryweather et al., (2011) 

found that MSTC increased significantly when walking on 

irregular surfaces compared to level walking.23 Similarly, we 

found that able-bodied participants adapted their MSTC to 

different walking conditions, either by increasing ankle or 

hip angle. However, there were no significant differences in 

knee angle between level walking and other conditions, 

except during upslope walking where knee angle increased 

approximately 14 degrees (38.8 (SD = 4.5) versus 25.4 (SD 

= 5.1)) at the point of MSTC. This was expected since 

incline walking requires the foot to be raised and then 

contact the ground above the stance limb. People with 

transtibial amputation also adapted their gait on more 

challenging walking conditions; however, there were no 

significant differences in MSTC between level walking and 

other conditions. The lowest MSTC for amputee and control 

groups was when the limb was at the top of the cross-slope; 

therefore, the probability of a stumble scenario on top cross-

slopes might be greater than other walking conditions. In the 

current study, platform tilts to the right or left with a 5° slope; 

thus, different angles of cross-slope should be tested to 

determine the risk of tripping in able-bodied and people with 

transtibial amputation.  

Maximum MSTC and knee angle occurred during down 

slope for the vacuum ON and OFF. Similarly, the literature 

showed that knee flexion increased during down slope 

walking since the prosthetic foot (heel) is not able to deform 

effectively to reach foot-flat.24 Amputees in the current study 

typically had larger MSTC than the able-bodied individuals, 

therefore MSTC was sufficient to clear the ground and 

possibly reduce tripping probability. Based on the literature, 

knee extensors and flexors strength in the amputated side 

is reduced in comparison with the intact side.25,26 Moreover, 

loss of muscles, tendons, and active ankle 

dorsiflexion/plantarflexion in the amputated side may 

compromise function and proprioception.27 Therefore, we 

had expected to have larger MSTC on the intact side 

compared to the prosthetic side with active (ON) or inactive 

vacuum (OFF). However, we found larger MSTC in the 

prosthetic side than the intact side and the able-bodied 

individuals. This larger MSTC in prosthetic side could be an 

anticipatory strategy used by people with amputation. 

Previous research also suggested that, compared to young 

individuals, older adults actively increase foot clearance as 

an anticipatory strategy  to reduce the risk of contact 

between the toes and the ground which could cause 

tripping/falling.28,29 Sensinger et al., (2012) also indicated 

that prosthesis users use different strategies such as 

vaulting and hip hiking to compensate for inadequate toe 

clearance.30 Larger MSTC in people with transtibial 

amputation in the current study might also be due to these 

protective strategies for clearing the ground safely.  

Appropriate swing toe clearance could be achieved by 

reducing effective lower limb length via synchronized ankle, 

knee, and hip flexion.20 One study suggested that 

increasing hip flexion could increase MSTC.6 The current 

study showed that able-bodied individuals had larger hip 

angle than the amputee group; nevertheless, MSTC was 

smaller in the able-bodied group. Moosabhoy and Gard 

(2006) found that knee and hip have fewer effects on MSTC 

than ankle.31 Similarly, we found no correlation between 

MSTC and hip angle for amputee and able-bodied groups, 

whereas higher correlations were found between ankle 

angle and MSTC in the amputee’s intact side.  

0

0.5

1

1.5

2

2.5

3

3.5

LW DS US HL TS BS ML RO

M
S

T
C

 (
c
m

)

Walking conditions

Able-bodied Vacuum ON Vacuum OFF

https://doi.org/10.33137/cpoj.v5i1.36847


 

6 

Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics & 
Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

ISSN: 2561-987X 
EFFECTS OF PROSTHETIC SUSPENSION SYSTEM ON SWING TOE CLEARANCE 

Gholizadeh et al., 2022 CPOJ 

 

Prosthetic elevated vacuum suspension system could 

improve socket fit and proprioception, which could enhance 

gait symmetry in people with transtibial amputation.12,32 

Similarly, our previous study showed better proprioception 

and greater comfort for Unity users with vacuum ON 

compared to vacuum OFF.15 The current study showed 

non-significant increase of the knee and hip angles in most 

walking conditions when the vacuum was OFF compared to 

vacuum ON. Increased knee and hip angles could be an 

anticipatory strategy used by amputees, possibly due to 

less proprioception with vacuum OFF, to ensure enough toe 

clearance. This should be further investigated with a larger 

number of participants. A high functioning transtibial 

amputees group with K3 and K4 activity level33 participated 

in the current study. Future research should examine effects 

of the Unity suspension system on MSTC for lower activity 

level (K1-K2) to assist in clinical decision-making. One 

month of accommodation was provided for the Unity 

suspension system, but no accommodation period was 

provided for the vacuum OFF condition. Using the 

prosthesis with vacuum OFF for hours or longer may affect 

limb volume and socket comfort, where discomfort and 

inappropriate socket function could affect the gait. 

Therefore, we only evaluated the immediate effect of 

vacuum OFF during testing by detaching the distal Unity 

tube and removing negative pressure inside the socket.  

CONCLUSION 

Effective prosthetic suspension system could improve 

MSTC and might decrease the risk of tripping and falling. 

The results of this study showed that active people with 

transtibial amputation could have appropriate MSTC during 

gait, when using the Unity suspension system. This 

prosthetic configuration could reduce anticipatory strategies 

to compensate for the absence of a controllable prosthetic 

ankle joint. 

ACKNOWLEDGEMENTS 

The authors would like to thank Knut Lechler for providing clinical 

and technical advice and support. Emily Sinitski, and Courtney 

Bridgewater are thanked for assistance with clinical testing. 

DECLARATION OF CONFLICTING 

INTERESTS 

The authors declare that there is no conflict of interest.  

AUTHOR CONTRIBUTION 

• Hossein Gholizadeh: study design, data collection, data 

analyses and writing of the manuscript. 

• Edward D. Lemaire: study design, supervision, review and 

editing of the manuscript.  

Table 4: Correlation between MSTC, knee, and hip angles. Correlations greater than 0.5 (moderate and strong correlation) are in bold. 

Confidence intervals are presented in parentheses.  LW: Level; DS: Down slope; US: Up slope; HL: Hilly; TS: Top cross-slope; BS: Bottom 

cross-slope; ML: Medio-Lateral; RO: Rocky. 
 

INTACT PROSTHETIC 

MSTC-Ankle MSTC-Knee MSTC-Hip MSTC-Knee MSTC-Hip 

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LW 0.65* (0.121, 0.891) 0.15 (-0.464, 0.667) 0.33 (-0.301, 0.760) -0.01 (-0.581, 0.567) 0.27 (-0.360, 0.731) 

DS 0.69* (0.192, 0.905) 0.51 (-0.090, 0.838) 0.44 (-0.179, 0.809) -0.15 (-0.667, 0.464) -0.12 (-0.649, 0.487) 

US 0.10 (-0.503, 0.637) 0.54 (-0.049, 0.850) 0.47 (-0.142, 0.822) -0.23 (-0.710, 0.396) 0.07 (-0.525, 0.619) 

HL 0.48 (-0.130, 0.826) -0.26 (-0.726, 0.369) 0.07 (-0.525, 0.619) -0.28 (-0.736, 0.350) 0.25 (-0.378, 0.721) 

TS -0.31 (-0.750, 0.321) 0.09 (-0.510, 0.631) -0.30 (-0.746, 0.331) 0.12 (-0.487, 0.649) 0.39 (-0.237, 0.788) 

BS 0.50 (-0.104, 0.834) 0.19 (-0.431, 0.689) 0.27 (-0.360, 0.731) -0.22 (-0.705, 0.405) 0.05 (-0.539, 0.607) 

ML 0.32 (-0.311, 0.755) -0.10 (-0.637, 0.503) 0.17 (-0.448, 0.678) 0.25 (-0.378, 0.721) 0.16 (-0.456, 0.672) 

RO 0.42 (-0.203, 0.801) 0.48 (-0.130, 0.826) 0.19 (-0.431, 0.689) -0.14 (-0.661, 0.472) 0.10 (-0.503, 0.637) 

      

U
n
it
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F
F

 

LW 0.76* (0.330, 0.929) 0.35 (-0.280, 0.769) 0.34 (-0.291, 0.765) 0.52 (-0.077, 0.842) 0.43 (-0.191, 0.805) 

DS 0.53 (-0.063, 0.846) 0.39 (-0.237, 0.788) 0.48 (-0.130, 0.826) 0.28 (-0.350, 0.736) 0.34 (-0.291, 0.765) 

US 0.74* (-0.063, 0.846) 0.58* (0.009, 0.866) -0.02 (-0.587, 0.560) 0.47 (-0.142, 0.822) -0.05 (-0.607, 0.539) 

HL 0.78* (0.373, 0.935) 0.57* (-0.006, 0.862) 0.36 (-0.270, 0.774) 0.73* (0.269, 0.919) 0.44 (-0.179, 0.809) 

TS 0.54 (-0.049, 0.850) 0.38 (-0.248, 0.783) 0.14 (-0.472, 0.661) 0.37 (-0.259, 0.779) 0.09 (-0.510, 0.631) 

BS 0.69* (0.192, 0.905) -0.41 (-0.796, 0.214) 0.12 (-0.487, 0.649) 0.26 (-0.369, 0.726) 0.23 (-0.396, 0.710) 

ML 0.83* (0.489, 0.951) 0.50 (-0.104, 0.834) 0.36 (-0.270, 0.774) 0.62* (0.072, 0.881) 0.25 (-0.378, 0.721) 

RO 0.56 (-0.020, 0.858) 0.22 (-0.405, 0.705) 0.11 (-0.495, 0.643) -0.39 (-0.788, 0.237) 0.16 (-0.456, 0.672) 

      

1
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LW 0.49 (-0.117, 0.830) 0.24 (-0.387, 0.715) 0.15 (-0.464, 0.667)   

DS 0.35 (-0.280, 0.769) 0.09 (-0.510, 0.631) -0.12 (-0.649, 0.487)   

US 0.45 (-0.167, 0.814) 0.30 (-0.331, 0.746) 0.09 (-0.510, 0.631)   

HL 0.09 (-0.510, 0.631) -0.15 (-0.667, 0.464) -0.03 (-0.594, 0.553)   

TS 0.35 (-0.280, 0.769) 0.10 (-0.503, 0.637) -0.01 (-0.581, 0.567)   

BS 0.40 (-0.226, 0.792) -0.27 (-0.731, 0.360) -0.13 (-0.655, 0.480)   

ML 0.42 (-0.203, 0.801) 0.33 (-0.301, 0.760) -0.05 (-0.607, 0.539)   

RO 0.43 (-0.191, 0.805) 0.17 (-0.448, 0.678) 0.35 (-0.280, 0.769)   

 

https://doi.org/10.33137/cpoj.v5i1.36847


 

7 

Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics & 
Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

ISSN: 2561-987X 
EFFECTS OF PROSTHETIC SUSPENSION SYSTEM ON SWING TOE CLEARANCE 

Gholizadeh et al., 2022 CPOJ 

 
• Julie Nantel: study design, supervision, review and editing 

of the manuscript.  

SOURCES OF SUPPORT 

This study was financially supported by Mitacs and Össur. All 

prosthetics components were provided by Össur. 

ETHICAL APPROVAL 

The Ottawa Hospital Research Ethics Board approved the study 

protocol and all participants provided written informed consent.    

REFERENCES 

1.Winter DA. Biomechanics and motor control of human gait: 

normal, elderly and pathological. 1991.  

2.Mills PM, Barrett RS. Swing phase mechanics of healthy young 

and elderly men. Hum Mov Sci. 2001;20(4–5):427–46. DOI: 

10.1016/s0167-9457(01)00061-6 

3.Winter DA. Foot trajectory in human gait: a precise and 

multifactorial motor control task. Phys Ther. 1992;72(1):45–53. 

DOI: 10.1093/ptj/72.1.45 

4.Winter DA, Patla AE, Frank JS, Walt SE. Biomechanical walking 

pattern changes in the fit and healthy elderly. Phys Ther. 

1990;70(6):340–7. DOI: 10.1093/ptj/70.6.340 

5.Eshraghi A, Osman NAA, Gholizadeh H, Karimi M, Ali S. 

Pistoning assessment in lower limb prosthetic sockets. Prosthet 

Orthot Int. 2012;36(1):15–24. DOI: 10.1177/0309364611431625 

6.Johnson L, De Asha AR, Munjal R, Kulkarni J, Buckley JG. Toe 

clearance when walking in people with unilateral transtibial 

amputation: effects of passive hydraulic ankle. J Rehabil Res Dev. 

2014;51(3):429-37. DOI: 10.1682/JRRD.2013.05.0126 

7.Lechler K, Kristjansson K. The importance of additional mid swing 

toe clearance for amputees. Can Prosthet Orthot J. 2018;1(2). 

DOI:10.33137/cpoj.v1i2.30813 

8.Gholizadeh H, Osman NA, Kamyab M, Eshraghi A, Abas WW, 

Azam MN. Transtibial prosthetic socket pistoning: Static evaluation 

of Seal-In® X5 and Dermo® Liner using motion analysis system. 

Clin Biomech. 2012;27(1):34–9. DOI: 10.1016/j.clinbiomech.2011. 

07.004 

9.Baars ECT, Geertzen JHB. Literature review of the possible 

advantages of silicon liner socket use in trans-tibial prostheses. 

Prosthet Orthot Int. 2005;29(1):27–37. DOI: 10.1080/ 

17461550500069612 

10.Gholizadeh H, Lemaire ED, Eshraghi A. The evidence-base for 

elevated vacuum in lower limb prosthetics: Literature review and 

professional feedback. Clin Biomech. 2016;37:108–16. DOI: 

10.1016/j.clinbiomech.2016.06.005 

11.Xu H, Greenland K, Bloswick D, Zhao J, Merryweather A. 

Vacuum level effects on gait characteristics for unilateral transtibial 

amputees with elevated vacuum suspension. Clin Biomech. 

2017;43:95–101. DOI: 10.1016/j.clinbiomech.2017.02.008 

12.Board WJ, Street GM, Caspers C. A comparison of trans-tibial 

amputee suction and vacuum socket conditions. Prosthet Orthot 

Int. 2001;25(3):202–9. DOI: 10.1080/03093640108726603 

13.Thibault G, Gholizadeh H, Sinitski E, Baddour N, Lemaire ED. 

Effects of the unity vacuum suspension system on transtibial gait 

for simulated non-level surfaces. PloS One. 2018;13(6):e0199181. 

DOI: 10.1371/journal.pone.0199181 

14.Gholizadeh H, Lemaire ED, Sinitski EH. Transtibial amputee gait 

during slope walking with the unity suspension system. Gait 

Posture. 2018;65:205–12. DOI: 10.1016/j.gaitpost.2018.07.059 

15.Gholizadeh H, Lemaire ED, Sinitski EH, Nielen D, Lebel P. 

Transtibial amputee gait with the unity suspension system. Disabil 

Rehabil Assist Technol. 2020;15(3):350-356. DOI: 10.1080/ 

17483107.2019.1579000 

16.Sinitski EH, Lemaire ED, Baddour N, Besemann M, Dudek NL, 

Hebert JS. Fixed and self-paced treadmill walking for able-bodied 

and transtibial amputees in a multi-terrain virtual environment. Gait 

Posture. 2015;41(2):568–73. DOI: 10.1016/j.gaitpost.2014.12.016 

17.Gates DH, Dingwell JB, Scott SJ, Sinitski EH, Wilken JM. Gait 

characteristics of individuals with transtibial amputations walking on 

a destabilizing rock surface. Gait Posture. 2012;36(1):33–9. DOI: 

10.1016/j.gaitpost.2011.12.019 

18.Young PMM, Wilken JM, Dingwell JB. Dynamic margins of 

stability during human walking in destabilizing environments. J 

Biomech. 2012;45(6):1053–9. DOI: 10.1016/j.jbiomech.2011.12. 

027 

19.Begg R, Best R, Dell’Oro L, Taylor S. Minimum foot clearance 

during walking: strategies for the minimisation of trip-related falls. 

Gait Posture. 2007;25(2):191–8. DOI: 10.1016/j.gaitpost.2006. 

03.008 

20.Sinitski EH, Lemaire ED, Baddour N, Besemann M, Dudek N, 

Hebert JS. Maintaining stable transtibial amputee gait on level and 

simulated uneven conditions in a virtual environment. Disabil 

Rehabil Assist Technol. 2021;16(1):40–8. DOI: 10.1080/ 

17483107.2019.1629186 

21.Rosenblatt NJ, Bauer A, Rotter D, Grabiner MD. Active 

dorsiflexing prostheses may reduce trip-related fall risk in people 

with transtibial amputation. J Rehabil Res Dev. 2014;51(8). DOI: 

10.1682/JRRD.2014.01.0031 

22.Miller WC, Speechley M, Deathe B. The prevalence and risk 

factors of falling and fear of falling among lower extremity 

amputees. Arch Phys Med Rehabil. 2001;82(8):1031–7. DOI: 

10.1053/apmr.2001.24295 

23.Merryweather A, Yoo B, Bloswick D. Gait characteristics 

associated with trip-induced falls on level and sloped irregular 

surfaces. Minerals. 2011;1(1):109–21. DOI:10.3390/min1010109 

24.Fradet L, Alimusaj M, Braatz F, Wolf SI. Biomechanical analysis 

of ramp ambulation of transtibial amputees with an adaptive ankle 

foot system. Gait Posture. 2010;32(2):191–8. DOI: 10.1016/ 

j.gaitpost.2010.04.011  

25.Fontes CH da S, Laett CT, Gavilão UF, Campos JC de, 

Alexandre DJ de A, Cossich VR, et al. Bodyweight distribution 

between limbs, muscle strength, and proprioception in traumatic 

transtibial amputees: a cross-sectional study. Clinics. 2021;76. 

DOI: 10.6061/clinics/2021/e2486 

26.Isakov E, Burger H, Gregorič M, Marinček C. Isokinetic and 

isometric strength of the thigh muscles in below-knee amputees. 

Clin Biomech. 1996;11(4):233–5. DOI: 10.1016/0268-0033(95) 

00078-x 

https://doi.org/10.33137/cpoj.v5i1.36847


 

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Gholizadeh H, Lemaire E.D, Nantel J. Effects of unity prosthetic elevated vacuum suspension system on minimum swing toe clearance. Canadian Prosthetics & 
Orthotics Journal. 2022; Volume 5, Issue 1, No.1. https://doi.org/10.33137/cpoj.v5i1.36847 

ISSN: 2561-987X 
EFFECTS OF PROSTHETIC SUSPENSION SYSTEM ON SWING TOE CLEARANCE 

Gholizadeh et al., 2022 CPOJ 

 
27.Smith DG, Fergason JR. Transtibial amputations. Clin. Orthop. 

Relat. Res. 1999;361:108-15.  

28.Mills PM, Barrett RS, Morrison S. Toe clearance variability 

during walking in young and elderly men. Gait Posture. 

2008;28(1):101–7. DOI: 10.1016/j.gaitpost.2007.10.006 

29.Sparrow WA, Begg RK, Parker S. Variability in the foot-ground 

clearance and step timing of young and older men during single-

task and dual-task treadmill walking. Gait Posture. 2008;28(4):563–

7. DOI: 10.1016/j.gaitpost.2008.03.013 

30.Sensinger JW, Intawachirarat N, Gard SA. Contribution of 

prosthetic knee and ankle mechanisms to swing-phase foot 

clearance. IEEE Trans Neural Syst Rehabil Eng. 2012;21(1):74–

80. DOI: 10.1109/TNSRE.2012.2224885 

31.Moosabhoy MA, Gard SA. Methodology for determining the 

sensitivity of swing leg toe clearance and leg length to swing leg 

joint angles during gait. Gait Posture. 2006;24(4):493–501. DOI: 

10.1016/j.gaitpost.2005.12.004 

32.Ferreira AEK, Neves EB. A comparison of vacuum and KBM 

prosthetic fitting for unilateral transtibial amputees using the Gait 

Profile Score. Gait Posture. 2015;41(2):683–7. DOI: 10.1016/ 

j.gaitpost.2015.01.026 

33.Gailey RS, Roach KE, Applegate EB, Cho B, Cunniffe B, Licht 

S, et al. The amputee mobility predictor: an instrument to assess 

determinants of the lower-limb amputee’s ability to ambulate. Arch 

Phys Med Rehabil. 2002;83(5):613–27. DOI: 10.1053/ampr. 

2002.32309 

 

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